Commutator-brush.



H. K. SANDELL.

COMMUTATOR BRUSH.

APPLICATION men MAR. 20, 1916.

1 ,222,999. Patented Apr. 17,1917.

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UNITED STATES PATENT OFFICE.

HENRY K. SANDELL, OF CHICAGO, ILLINOIS, ASSIGNOR TO HERBERT S. MILLS, OF

. CHICAGO, ILLINOIS.

COMMUTATQR-BRUSH.

Application filed March 20, 1916. Serial No. 85,322.

To all whom it may concern:

Be it known that I, HENRY K. SANDELL, a citizen of the United States,

of Cook and State of Illinois, have invented a new and useful Improvement in Commutator-Brushes, of which the followingis a specification.

My invention relatesto certain new and useful improvements in commutator brushes.

The primary object of the inventionis to 'provide a brush of high current-carrying capacity andlong life and which will not wear seize or unduly wear the surface of the commutator. While these attributes are to some extent common to all cast metal brushes they are, in the case of many metals, linked with disadvantageous" properties such as low conductivity, or a tendency to spark or to throw off incandescent particles.

I have found that by the use of certain metals or alloys I may obtain the desired highly crystalline structure without sacrifice of any of the essential properties. The base metal which I have found best suited to these requirements is copper. For harden-- ing the copper and giving to it the highest degree of crystalline structure without unduly lowering its conductivity I make use of a certain proportion of antimony. I

find it furtherdesirable to use a proportion of a third metal or metals, such as nickel, lead and tin which appear to serve as a hinder or toughener, reducing the wear of the brush by preventing the disintegration of the contact surface under friction.

In applying these principles I obtain satis- Specification 01 Letters ram.

residing at 221v South Green street, Chicago, in the county Patented Apr. 17, 1917.

factory results from cast brushes of the following compositions Parts by weight. (1.) Copper 2 -Antimony l 4 (2.) Copper 8 Antimony 2 Tin 1 '(3.) Copper s 4 Antimony 2 Lead 1 (4.) Copper 8 Antimony 4 %ickel 2 5. 0 er 8 Ani i fnony 4 Nickel 1 Lead 1 All of these formulae provide brushes of high conductivity and satisfactory wearing properties, both as regards the brush per so and the commutator. For the service for which I have particularly. designed my brushes, 2'. 0., for mechanically rectifying alternating current by a commutator driven from a synchronous motor, the last formula seems to be the best. Formulae numbered 3 and 4 seem to be about equally good as between themselves, and bothslightly inferior to formula 5, formula two is next best, and formula one least desirable, but

nevertheless quite serviceable.

In the particular service which I have mentioned it is not only desirable that the .brush be of high conductivity in order that it may be of small cross-section and therefore of small depth without being necessarily of inordinate width, but it is further desirable that the weight of the brush. be kept at the lowest point, for the reason that the most perfect commutator is not absolutely true, or at least does not remain so, and by its rotation at high speeds therefore tends to kick the brush outward as the points of eccentricity pass under the same.

The time and angular travel of the commutator required to permit the brush to again seat itself after having been kicked off will be a function of the mass of the brush and of the force exerted by the spring which feeds the brush inwardly. To increase the tension of this spring is to increase the friction of and wear upon the brush and commutator, and it is therefore quite clear that the most advantageous results may be obtained by decreasing the mass of the brush. I accordingly prefer to construct my cast brush in two sections; a wearing or surface section of highly conductive cast metal and a guide or supporting section of light metal such as aluminum, to which the conductor wire or pig-tail is attached. These two sections are united, preferably by welding their abutting ends, so that the finished brush is an integral member, presenting the appearance shown by the accompanying drawing in which proper legends are applied to the two sections and to the point at Which they are joined.

In constructing such a brush the preferred mode of procedure is to first cast the aluminum guide section, the pigtail being cast therein if desired, and to then lay this section in proper position in a brush mold, pouring in the molten alloy which is to constitute the operative portion of the brush. The parts will thus be welded together in the act of casting and the brush may beremoved from the mold and machined or ground to finished form as a unit.

What I claim as new and desire to secure by Letters Patent is:

1. A brush cast from an alloy comprising copper, antimony and nickel.

2. A brush cast from an alloy comprising more than fifty per cent. of'copper, about thirty per cent. of antimony, and more than five per cent. of nickel.

3. A brush cast from an alloy comprising copper, antimony, nickel and lead.

4-. A brush cast from an alloy comprising more than fifty per cent. of copper, and about forty per cent. of antimony, nickel and lead taken together.

5. A brush cast from an alloy comprising about copper, about antimony, and about of nickel and lead taken together.

6. A brush cast from an alloy consisting of 8 parts copper, 4 parts antimony and one part each of lead and nickel.

7 A'brush comprising two abutting sections of different composition joined to form an integral member, the wearing end section being of relatively heavy material and the guide end section being of relatively light material.

8. A metallic brush comprising, two abutting sections of different metals joined to form an integral member, the wearing end section being of relatively heavy metal and the guide end section of relatively light metal.

9. A metallic brush comprising two abutting sections of different metals joined to form an integral member, the Wearing end section being of copper alloy and the guide end section of aluminum.

10. An integral cast metal brush comprising a wearing end section of copper alloy and a guide end section of aluminum.

'- HENRY K. SANDELL 

